The invention relates to a ceramic-coated metal implant for use in medicine a hemiprosthesis and endoprosthesis.
Known implants are made out of metals or metal alloys, such as titanium, tantalum, chromium-cobalt-molybdendum alloys and materials such as carbon, polymers or alumminum oxide ceramics or combinations thereof.
An improvement of the characteristics of an implant has been attempted by means of specific surface treatments. In DE-OS No. 2,324,867 the biocompatibility of a metal implant is temporarily improved by storing ions in the surface of the metal implant. Due to diffusion, however, a short time after implanting, harmful ions enter into the implant bed and, thus, it cannot be assured that the implant will stay in place for a long time.
DE-OS No. 2,838,759 has the aim of rendering the surface of an implant passive by means of sophisticated vacuum techniques. layers applied with this technique are very thin and do not adhere very well and, thus, have a negative influence on the in-situ period for the implant.
EP No. 0023608 describes a bioreactive calcium phosphate ceramic which is pressed onto the surface of a metallic implant body by a pressing-sintering process. EP No. 006544 introduces an implantable metallic bone material on the surface of which spherical calcium phosphate particles are applied. This is achieved in that a calcium phosphate particles are adhered to the inside walls of mold which is then filled with metal. The same effect can be achieved by hot-pressing, flame-spraying or plasma-spraying.
The calcium phosphate ceramic applied in this way, however, can easily be leached out in the living body and, furthermore, is insufficiently adjusted to bone growth in its concentration supply and does not take into consideration required textural dimensions in order for tissue to grow into it. The period during which the implant can remain in place is therefore negatively influenced.
The literature (Strauss, V.E. Bild der Wissenschaft 2 (1984), 110-122) describes a compound ceramic-metal implant. The advantages of the ceramic should be simultaneously combined with the strength of the metal. The applied ceramic layers, however, do not sufficiently adhere to the metal. The surgically inserted implant is, therefore, severely limited as to the period during which it can stay in place.